1. Field of Art
This invention generally relates to the field of night vision systems, particularly to head or helmet mounted night vision systems.
2. Description of the Related Art
A night vision system improves the ability of a user to see in an environment where small amounts of light are present. Existing night vision systems take in low levels of ambient light not viewable to the naked eye and amplify it to viewable levels using image intensifier tubes. An image intensifier tube functions by amplifying the number of received photons while keeping the resulting photons spatially separated so that the original image formed by the ambient light is not distorted or blurred. The downside of image intensifier tubes, however, is that they are bulky and they are analog sensors. Existing night vision systems have a number of limitations caused by the physical characteristics of image intensifier tubes.
For example, existing night vision systems have large forward projection and have forward centers of gravity, which reduces their usability. In particular, pilots using existing systems have a restricted range of motion for their head and the forward center of gravity induces neck fatigue and is unsafe for ejection. When performing high gravity turns, the weight of the night vision system is multiplied by the g-loading generated by the turn. That weight is borne by the pilot in the head and neck area. A non-neutral center of gravity serves to magnify the weight felt by the pilot while in the turn, which causes the night vision system to move and may result in injury to the pilot.
Existing night vision systems typically also have a limited field of view, often around 40 degrees in both the horizontal and vertical directions. Increasing the field of view typically would require the use of multiple image intensifier tubes. The additional image intensifier tubes multiply the engineering constraints (including weight, space and power) of the system, along with any problems caused by those constraints. Further, they can introduce distortion in the night vision image viewed by the user at the boundary between the outputs of adjacent tubes. There is currently no way to remove the distortion in these systems.